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Generating hydrogen fuel from waste energy

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March 15, 2010

The new process breaks the chemical bonds in water using waste energy (Image: Jose Manuel ...

The new process breaks the chemical bonds in water using waste energy (Image: Jose Manuel Suarez)

We recently looked at a breakthrough in using sunlight to create hydrogen but now scientists have found a way to use ambient noise to turn water into usable hydrogen fuel. The process harvests small amounts of otherwise-wasted energy such as noise or stray vibrations from the environment to break the chemical bonds in water and produce oxygen and hydrogen gas.

Materials scientists at the University of Wisconsin-Madison grew nanocrystals of two common crystals, zinc oxide and barium titanate, and placed them in water. When pulsed with ultrasonic vibrations, the nanofibers flexed and catalyzed a chemical reaction to split the water molecules into hydrogen and oxygen.

When the fibers bend, asymmetries in their crystal structures generate positive and negative charges and create an electrical potential. This phenomenon, called the piezoelectric effect, has been well known in certain crystals for more than a century and is the driving force behind quartz clocks and other applications.

The researchers applied the same idea to the nanocrystal fibers. "The bulk materials are brittle, but at the nanoscale they are flexible," says UW-Madison geologist and crystal specialist Huifang Xu. He likened them to the difference between fiberglass and a pane of glass.

Smaller fibers bend more easily than larger crystals and therefore also produce electric charges easily. So far, the researchers have achieved an 18 percent efficiency with the nanocrystals, higher than most experimental energy sources.

In addition, Xu says, "because we can tune the fiber and plate sizes, we can use even small amounts of [mechanical] noise - like a vibration or water flowing - to bend the fibers and plates. With this kind of technology, we can scavenge energy waste and convert it into useful chemical energy."

Rather than harvest this electrical energy directly, the scientists took a novel approach and used the energy to break the chemical bonds in water and produce oxygen and hydrogen gas.

The chemical energy of hydrogen fuel is more stable than the electric charge, Xu explains. It is relatively easy to store and will not lose potency over time.

With the right technology, Xu envisions this method being useful for generating small amounts of power from a multitude of small sources - for example, walking could charge a cell phone or music player, and breezes could power streetlights.

"We have limited areas to collect large energy differences, like a waterfall or a big dam," he says. "But we have lots of places with small energies. If we can harvest that energy, it would be tremendous."

The UW-Madison team’s research appears in the Journal of Physical Chemistry Letters.

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag.   All articles by Darren Quick
4 Comments

Limited areas to collect large energy differences? It depends on the scales (large and small) possible. I would agree in the natural world, but humans have created a noisy planet. Trains create a large amount of vibration near the tracks as they travel. Airports are not quiet by any stretch of the imagination. Shopping malls are places where a lot of energy of this kind, as well as previous floor-generating piezio ones, could be used. Subways are just like trains. Tops of skyscrapers are almost always under a steady wind stronger than the average ground-level breeze. Construction sites are very loud, full of vibration, and need power of a transitory nature. Just some ideas off the top of my head.

CeridianMN
16th March, 2010 @ 12:12 pm PDT

Your point is exactly what the article concludes with Ceridian; there are lots of places/ways in which to gather otherwise wasted energy using this method: all the things you've listed would be categorised as `small energies' when compared to the kinetic energy of a waterfall or dam individually, but it's their cumulative energy that would be tremendous because as you so rightly say, there are so many of them.

earlleonard
16th March, 2010 @ 06:28 pm PDT

Since when is Hydrogen easy to store? In order to be useful, Hydrogen has to be stored either under high pressure, or large volume. High pressure obviously requires compressors and tanks that can handle 10,000 psi (or higher). Otherwise you need a really really really really (I think you get it) really big tank. Plus all these guys seem to ignore the fact that their methods will either oxidize their neato machine, or generate H2O2, an extremely explosive gas mixture. Nobody seems to mention how they plan to separate the oxygen gas from the hydrogen gas. Sorry, but I think it's still better to store the electricity than Hydrogen.

Eletruk
31st March, 2010 @ 10:22 am PDT

Hydrogen can be stored in metal hydride alloys under low pressures. In the 1970's a guy drove around in Australia in an old 67 Holden powered by H2 that was stored in an LP gas cylinder filled with these allow chunks, but as usual he was ignored. Anyway H2 powered vehicles ( combustion or fuelcel ) are now a going concern, so instead of lining the highways with 12 foot high timber walls to reduce the noise at great expense (not to mention the thousands of trees for the timber) --- erect walls containing this H2 producing crystals and pipe the H2 to filling stations along the highway and also build solar collectors near these filling stations as well

Jim60
31st March, 2010 @ 06:21 pm PDT
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